WRX Cold Weather Transmission Slip

Check your transmission fluid level. They are hard to fill right. (Do it several days in a row and you might find one day it is down a little.)

Sit in your driveway a minute or two with the engine running to get a little warmth in there or get a heater to plug the car in.

What you describe is more severe than my car is, but pretty much the same. (It delays shifting unless you are really pounding on it to go, after a block or two, it goes away.)

I assume that due to your driveway and road you can't just mope a long a block or two, but if you can alter your route to go slower at first it might help.

This issue has been discussed before.

The solution seems to be better engine warm up.

Let the car idle for 10 minutes or so, whatever is needed to nicely warm up the engine before taking-off. Apparently a warmer engine positively affects the transmission (helps it warm up faster also, I guess). Anyway, shifting problems on take-off may be greatly diminished.

MN

My understanding is the cooling system has runs that also cool the transmission.

So, engine heats coolant which heats the transmission when not moving.

If driving, friction will heat up the transmission pretty quickly.

According to MN :

A lot of the replies to my post seem to imply that the AT is not shifting from 1st to 2nd (because of the cold transmission). It doesn't feel that way to me, it feels like slipping. When I start out locked in 1st on a warm day, the car accelerates very hard up to redline. It isn't going all that fast at redline, but it feels different than the cold weather problem I've been seeing.

I could do an experiment to distinguish these two theories. A) Tonight I'm in warm weather: I'll start on a hill in 1st and floor it. B) Tomorrow I'm in the snow: I'll start on a hill in 1st and floor it. If the problem I felt was a lack of shifting, A) and B) should feel the same. I could also see what my speedometer said at redline.

In terms of transmission fluid level, it could get tricky. At one point the Subaru dealer overfilled my transmission and it was overflowing after driving in the mountains, leaving a smoky smell in the engine compartment. After searching through the history of the group I found a post where the advice given was to add a small amount little by little. I could try something like that.

And I will try the experiment of running the car in idle for a ten minutes.

On a more theorical level. How would the transmission fluid filter affect the transmission performance? I could see lower fluid pressure with a clogged filter and thicker (cold) fluid. Does the fluid pressure drive any mechanical actions in the AT. I thought the 4EAT was driven electro-mechanically (not via hydraulic pressure) and that it never completely locks up the torque converter. I'd like to learn more about how the stock setup works, for instance below I'm interested in possible upgrades.

I'd like some feedback on possible replacements for the torque converter when I go off warranty. My understanding is that the stock converter doesn't ever completely lock up and that there are replacement torque converters that will lock up under certain conditions. Perhaps I could get slightly better gas mileage from an upgrade like that. Am I on base with my understanding of the AT setup and are there any drawbacks to swapping out the stock torque converter for a 'lock-up' one?

Well, maybe they just look at the title of your post?

My suggestion was basically to eliminate the possibilty that this is purely a low temperature related issue. Subaru transmissions are known to be very sensitive to low temps and exhibit slow shifting when not adequately warmed up.

If you eliminate this simple possibility then I guess it would be easier to suspect a mechanical/slipping problem which you may very well have. Certainly at 90k miles it is a strong possibility.

MN

Couple of tips;

Filling little by little is what I did. I had it flushed and filled at the dealer (one would assume they know how to fill it) and it worked OK but was a little off. Then I checked it, and found it was off the bottom of the stick.

I put some in, drove for OK a few days, found it not so good anymore, and put more in.

Did that for a while and finally it stopped acting funny after I had put about .5 to .75 quart in total. All the while, the dip stick to measure said it was full one time, and not full enough the next time. So it is pretty easy to not fill it properly when considering there is only a few quarts in there in the first place.

So the stick is not a good indicator of fluid level... especially if you are dealing with filling in 20 degree weather. You have to repeatedly measure it to catch it "low" and fill slowly if it does show up low.

For the theoretical issue, yes fluid viscosity makes a huge difference.

Think about it like this, a small pipe with a balloon at each end filled with syrup. If you squeeze one balloon the other fills. There are several balances like this used to switch gears around in an automatic transmission. The engine "pushing" on the baloon at one end, and the gear setting control on the other baloon. When the engine stops "pushing" the gear setting drops to a higher gear as the "acceleration" is not there. If the syrup is cold, it is harder to squeeze, so the engine is pushing harder (your RPM goes up as you accellerate) but no shifting occurs because the "pushing" is working against the resistance of the fluid, not resistance of the road (the other balloon). So the other side does not switch properly... ending in it not shifting when you expect it to.

To complicate matters, slipping transmission could also be caused by fluid level being low as the torque converter is not getting an adequate flow against it. Likewise for a clogged filter. So, check the fill repeatedly. Get your filter and fluid changed if you haven't done that in the last 30k miles. It's cheaper than a new transmission. (Don't forget to re-test a bunch of times after they fill it as one test of fill is not enough to determine if it is full.)

So cold transmission with high viscosity (thick) fluid... to the system that shifts feels like you are REALLY STOMPING on the accelerator because the difference between one "side" and the other "side" is artificially high. So it doesn't shift because it thinks you are accellerating. Only, you aren't as the extra engine energy is being used to push the thicker than normal fluid.

The top links are ads, but the "How transmissions.." and "How torque converters... " and "how coooling systems..." are very informative in making the behavior of your Subie from a mystery to something to deal with.

This is not to say you don't have other problems, but chances are its just a little low and not quite warm enough and that is all.

For what it's worth, I had a '83 Saab 900 AT that exhibited exactly the same symptons. I let the dealer convince me it was a blah, blah, blah issue. I ended up keeping the car 15 years and the only reason I got rid of it was that the AT was slipping so often that it was unsafe.

Moral of the story, if it's under warranty, get it fixed. Things only go downhill from where you are at.

Bob

Edward Elhauge wrote:

Definitely take the car in and have it checked, if for nothing else than to get the problem on the record under warranty. If a problem pop up after the warranty period is over there's a good chance, because you now have the problem on record, it will get fixed for free.

I know that the transmissions are made to shift differently when cold, and then go to normal when warmed up, but yours sounds a bit out of the norm. Some people have resolved the problem by having the tranny flushed and filled with synthetic fluid. The new gizmos they have today flush the system completely, so it's not like simply draining out a few drops and then refilling it like the old days.

Keep us posted. It's very frustrating when you have a great car and are constantly told a problem is "normal."

My Porsche shifts like stirring a bucket of tar with a stick. "Normal" for this model and 5 spd tranny. Fun to drive, but...